Is it permissible to take some hair from the sides and leave the back to grow long, in emulation of the Prophet, peace and blessings be upon him, with the intention of lengthening it to the ears?

Lengthening the hair for men and honoring it is from the Sunan (practices) of habits. The hair of the Prophet, peace and blessings be upon him, was all of a uniform length. Whoever wishes to follow his guidance in this should ensure that his hair is of equal length. There is no harm in shortening the sides of the head while leaving the back long, as long as it does not involve shaving.